折叠式群伞充气接触的膜索非线性有限元算法

Membrane-cable-based nonlinear finite element method for inflation and contact problem of folded parachute cluster

降落伞由折叠到打开的充气过程和多束降落伞捆绑在一起充气的过程都伴随着一个高度非线性的柔性结构接触问题,因此模拟降落伞群伞流固耦合问题必须首先解决降落伞群伞非线性结构接触的数值模拟问题。对于降落伞这类柔性瞬变非线性织物结构,数值模拟织物系统的接触现象以及预测接触结果对降落伞工作状况的影响对于降落伞群伞设计具有很重要的指导意义。基于三维降落伞膜索非线性有限元编程模拟技术设计了一种针对单伞和群伞非线性动力系统的接触搜索算法,推导设计了针对接触随机性的接触切线刚度矩阵计算方法。针对降落伞群伞非线性有限元计算的庞大数值计算量,设计编写了一种基于消息传递接口(MPI)通信协议的膜索结构并行接触模拟FORTRAN程序,测试了该数值模拟程序的并行计算效率。针对高度折叠的C-9降落伞群伞充气问题,使用PC-Cluster计算机群进行了数值仿真模拟,验证了该接触非线性有限元程序的计算效果,预测了C-9降落伞群伞的接触过程,并分析接触现象对降落伞群伞充气工作的影响。

The inflation process of a single parachute from the initial folded configuration as well as the inflation of a parachute cluster tied at the bottom node is always coupled with a highly nonlinear contact phenomenon for that kind of thin flexible fabric structures.Conduction of numerical fluid-structure interaction simulation of parachute cluster must first figure out how to simulate nonlinear structural contact problem by applying proper numerical method.According to the transient and nonlinear dynamic behavior of parachute fabric system,using numerical method to predict parachutes＇ contact phenomenon and analyze the influence of contact mechanism for thin fabric structures will provide important meaning during parachute cluster designing.Based on the three-dimensional membrane-cable nonlinear finite element analysis code,a nonlinear contact algorithm for single folded parachute as well as parachute cluster is presented.In order to simulate arbitrary contact problems during inflation,a computation method for contact tangent stiffness matrix is also proposed in this paper.Because of the large scale of computation during nonlinear finite analysis of parachute cluster inflation,aparallel computation technique based on message passing interface（MPI）standard for membrane-cable structures is designed and coded by FORTRAN to solve this kind of problem.Finally,numerical simulations for highly folded C-9parachute cluster inflation are carried out on a PC-Cluster computer group to verify the ability and efficiency of this new computational program and predict the contact phenomenon during inflation;the influence of contact mechanism has also been analyzed for the parachute cluster system.